New electrode materials derived from polyquinonic ionic compounds and their use in electrochemical generators

ABSTRACT

The present invention is concerned with novel compounds derived from polyquinonic ionic compounds and their use in electrochemical generators.

FIELD OF THE INVENTION

The present invention is concerned with novel polyquinonic ioniccompounds useful as electrode materials used for example inelectrochemical generators.

BACKGROUND OF THE INVENTION

Electrode materials derived from transition metals, in particulartransition metals binary chalcogenides, such as TiS₂, VO_(x) (2≦x≦2.5),ternary oxides such as LiNiO₂LiCoO₂, Li_(1+x)Mn_(2−x)O₄(0≦x≦1), etLiV₃O₈, are known. These materials are however often relatively toxic.With the exception of vanadium derivatives, the capacities arepractically modest, i.e. on the order of 100 Ah.g⁻¹, and their potential(about 4 V vs Li⁺/Li^(o) are beyond the domain of stability of solid orliquid electrolytes. They are therefore problematic in terms of safety.

Organic compounds like conjugated polymers work through an insertionmechanism of anions taken from the electrolyte. The mass capacitiesresulting therefrom are consequently low and the cycling possibilitiesare disappointing.

Other known compounds are those of the polydisulfide type, which, evenif they do not have intrinsic electronic conductivity, possessinteresting redox properties and mass capacities ((≧300 Ah.g⁻¹),particularly oxidizing coupling derivatives of2,5-dimercaptothiadiazole. However, the resulting reduction products andintermediates are lithium salts like conjugated thiolates with anitrogen atom. Delocalization of the charge on the polarisable anioniccenters like sulfur and nitrogen, lead to a relatively importantsolubility in the electrolytes, as well as a reduced cycling life span.

Monoquinones are organic compounds known for their redox properties, butthe potentials are of little interest (on the order of 2.2 V vs.Li⁺/Li^(o)), and the neutral oxidized compounds are soluble in theelectrolytes. Polymers bearing quinonic functions such as thoseresulting from hydroquinone and formaldehyde polycondensation, are notelectrochemically active because of the reduced mobility of the chargecarriers, ions and electrons, in the absence of highly polar proticsolvents like water.

SUMMARY OF THE INVENTION

The present invention concerns electroactive compounds derived fromanion salts bearing at least 2 quinone functions cumulated, conjugated,or both, in the same molecule. More specifically, the inventioncomprises a redox compound having at least one state of oxidation staterepresented by the general formula:

wherein

M⁺ represents an alkaline metallic cation, an alkaline-earth cation, atransition metal cation, a rare earth cation, an organometallic cation,an organic cation of the “nium” type, a repetitive unit of a cationicoxidized conjugated polymer, or a monomeric or polymeric cationoptionally having a redox character;

X is oxygen, NCN, or C(CN)₂;

Z is C—Y⁻ or N⁻;

Y represents oxygen, sulfur, NCN, —C(CN)₂, with the proviso that when Yis sulfur and n is ≦4, then X is oxygen;

R₁ is absent, O, S, NH, —(C═C)_(r), —(W═W)_(r)— wherein W isindependently CR⁶ or N; r varies between 1 and 12; and R⁶ is H, halogen,CN, or C₁₋₁₂ alkyl, C₂₋₁₂ alkenyl or C₆₋₁₄ aryl optionally having one ormore substituents oxa, aza or thia; and wherein 2 R⁶ groups can bebonded to form a cycle comprising from 3 to 7 members;

R² and R³ are the same or different and are absent, a carbonateddivalent radical, optionally substituted with aza, oxa or thia;

q varies between 0 et p;

p varies between 1 and 5;

n varies between 1 and 10⁴; and

wherein two of R¹, R² and R³ can be bonded together to form a cyclecomprising 3 to 7 members.

For the purposes of the present invention, when n is 4 or less, thecompound of the invention is not considered a polymer. In addition, theexpression “divalent radical” is defined as an alkylene, an arylene, oran arylalkylene of from 2 to 200 carbon atoms, and optionally comprisingone or more substituents aza, oxa or thia.

The present application further concerns an electrode materialcharacterized in that it contains, in whole or in part, a compound ofthe invention, and an electrical energy storage system such as a primaryor secondary generator or a super capacity comprising an electrolyte, atleast one negative electrode and at least one positive electrodecomprising a compound of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, a new family of electroactive compoundsderived from anion salts bearing a plurality of quinone functionscumulated and/or conjugated in the same molecule is described andclaimed. It has been found that such type of compounds have a highcapacity, i.e. equal or higher than 300 Ah.g⁻¹, obtained at potentialscomprised between 3.5 et 1 V vs. Li⁺/Li^(o), thus in the domain ofstability of conventional aprotic electrolytes, liquid or solid, andallowing the making of positive and negative electrodes for generators.Further, the corresponding salts do not, whatever their degree ofoxidation, solubilize significantly in liquid electrolytes or aproticpolymers. The kinetic of the redox reaction in solid phase is noticeableand comparable to that of inorganic insertion materials. It has alsobeen found that by replacing the oxygen atom of the neutral quinonicgroups CO with NCN groups or C(CN)₂, and/or the replacement of theoxygen atom of the quinonic groups negatively charged with anionicgroups NCN⁻ or C(CN)₂ ⁻ had the same interesting properties in terms ofthe redox activity. The redox potential is displaced of about 300 mVtowards the positive values by replacing a neutral quinonic oxygen withan NCN or C(CN)₂. The chemical methods to perform these substitutions onthe quinonic groups are well known to anyone of ordinary skill in theart.

The redox compounds of the present invention include also polyquinoneswherein the negatively charged oxygen of the quinonic groups is replacedwith sulfur S⁻. In this case, charge conjugation with an oxygenatedgroup CO neutral and weakly polarisable and more electronegative,significantly lowers the solubility of the corresponding ionicderivatives, in particular in electrolytic solutions. An additionaldegree of oxidation is then obtained by oxidative duplication of CS⁻groups to form disulfide bridges CS—SC.

These polyquinonic compounds can also be part of the polymers into whichthe charges are conjugated along the polymeric chain. In such a case,the solubility of these rigid macromolecules is null, whatever thecharge borne by the polymer, thus including the neutral state.

Because the compounds of the present invention are anion salts, i.e.,negatively charged, it is necessary to combine them with a cation inorder to have a global neutral charge. The preferred cations comprisethe proton, alkaline cations like Li, Na, K, Cs; alkaline-earth cationslike Mg, Ca, Ba; transition metal cations like Cu, Zn, Pb, Fe, Ni, Co,Mn, V, Cr; rare earth cations; organometallic cations likemetallocenium; cations of the <<ium>> type such as ammonium, amidinium,guanidinium, pyridinium, imidazolium, triazolium, imidazolinium,sulfonium, phosphonium, iodinium; a repetitive unit of an oxidizedcationic conjugated polymer such as polypyrrole, polythiophene,polyquinolines; cations in the form of monomers or polymers optionallyhaving a redox character such as viologenes of formula[—(R″NC₅H₄—C₅H₄N—)²⁺]_(n) wherein R″ comprises C₂₋₁₂ alkylene, C₆₋₁₄arylene or C₆₋₁₄ arylene C₂₋₁₂ alkylene, each optionally substitutedwith oxa, aza ou thia. The lithium cation and the proton areparticularly preferred. Other ions can be present in the electrolyticmedium and/or in the electrode material, and can contribute to improvethe conductivity of the interfacial properties. The potassium ion isadvantageously used in such instance, as well as cations derived fromquaternized imidazolium.

To the redox capacity of the molecules of the present invention can beadded that of the cation when the latter possesses many degrees ofoxidation. Cations of iron, copper or manganese, as well asmetallocenes, are particularly interesting for such application. Organiccations with redox properties, such as viologenes, are similarly useful.These cations can optionally be part of a polymeric chain.

The compounds of the present invention possess high specific capacitiesof redox exchange, and in fact superior to those of conventionalinorganic compounds. The great variety of functional groups availableallows choosing redox potentials in a wide range of potentials,typically between 0.1 to 3.7 V vs. Li⁺/Li^(o). Compounds with redoxcouples comprised between 0.1 and 2 V vs. Li⁺/Li^(o) are advantageouslyused as a component of negative electrodes in electrochemical generatorsof primary and secondary type batteries or supercapacitor. Similarly,compounds with redox couples comprised between 2 and 3.7 V vs.Li⁺/Li^(o) are advantageously used as component of positive electrodesin same devices or as an active or passive electrode in electrochromicdevices.

The compounds of the present invention can be used alone or in mixturesthereof. They can also be used in conjunction with other redoxcompounds, in particular insertion compounds. Such insertion compoundsinclude, for negative electrodes, metallic lithium or alloys thereof,optionally in the form of a nanometric dispersion in lithium oxide;double nitrides of lithium and a metal of transition such as cobalt;oxides with a low potential of general formula Li_(1+y)Ti_(2−x/4)O₄wherein x and y vary between 0 et 1; and carbon and carbonated productsresulting from the pyrolysis of organic matters. For the positiveelectrodes, the insertion compounds include oxides and sulfides oftransition metals, such as VO_(z) wherein z varies between 2 and 2.5;LiV₃O₈; Li_(a)N_(1−a)Co_(a)O₂ wherein a varies between 0 et 1; manganesespinels Li_(y)Mn_(2−x)M_(x)O₄ wherein x varies between 0 and 0.5 and yvaries between 0 and 2, and M is Li, Cr, Al, V, Ni; organicpolydisulfides; FeS; FeS₂; iron sulfate; iron and lithium phosphates andphosphosilicates of the olivine structure; or the substitution productof iron with manganese, either used alone or in mixtures.

The materials of the invention are particularly embodied in compositeelectrodes containing the novel redox compounds, alone or in mixtures,at least one electronic conductor, and at least one polymeric binder.The electronic conductors are preferably selected from carbonatedcompounds such as carbon black, graphite powder, products resulting fromthe pyrolysis of organic matters, in particular phenolic resins orpolyacrylonitrile. When the electrode binder does not have anyelectrochemical function but only a mechanical function, the latter isadvantageously chosen from non-polar polymers likepolytetrafluoroethylene, co- or ter-polymer of ethylene, propylene and adiene, that allow the binding of the materials while leaving a porositysufficient to permit the required electrolyte penetration for properoperation of these redox materials.

Liquid electrolytes suitable with such type of redox materials are thoseobtained by dissolving a salt or an acid in a solvent. The solvents arepreferably chosen from cyclic or acyclic carbonates, γ-butyrolactone,monoalkylamides and di-alkylamides, tetraalkylsulfamides, dialkylatedethers of mono, di, tri and tetraethylene glycols, as well as oligomershaving a mass lower than 2000 g/mole, and their mixtures.

In a variation, the electrode binder has an ionic conductivity andallows the maintenance of an intimate contact between the particles ofthe redox materials in the electrolyte while compensating, because oftheir plastic or elastomeric character, for the variations of volumeinherent to the operation of the electrode. In preferred embodiments,the electrolyte contains, individually or in a mixture, a polar-typepolymer, is a polar solvent, and/or at least one ionic salt. Thepolar-type polymers useful with the addition of a liquid solvent arepreferably selected from vinylidene fluoride-based homo- or copolymers,acrylonitrile-based homo- or copolymers, methyl methacrylate-based homo-or copolymers. The polar-type polymers useful with or without theaddition of a liquid solvent are preferably selected from polyetherssuch as ethylene oxide-based or propylene oxide-based homo- orcopolymers. In a variation of the preferred embodiment of the compoundsof the invention, ceramic or cross-linked particles are added to thepolymer electrolytes, to improve the mechanical properties.

Another interesting aspect of certain compounds of the invention istheir possibility to give, after oxidation beyond the normal reversibleoperating potential, an irreversible reaction liberating lithium ionsand gaseous compounds such as carbon monoxide or carbon dioxide,nitrogen, ethylene or acetylene and their polymers. These products areeliminated from the generator medium (gas) or are inactive (polymers),and provide exceeding capacity that is useful to compensate for the lossof capacity equilibrium between the anode and the cathode, caused mainlyby the appearance of a passivation layer during the first operatingcycles of the generator.

The following anions are illustrate compounds of the present invention,and should not be considered as limiting its scope.

The following examples are provided to illustrate preferred embodimentsof the present invention, and should not be considered as limiting itsscope.

Example 1

2.10 g of dihydrated rhodizonic acid (Lancaster Windham) are treatedwith 839 mg of monohydrate lithium hydroxide in isopropanol. Thesuspension is filtered and the black precipitate is dried under primaryvacuum at 50° C., to give the following lithium rhodizonate:

Example 2

A lithium battery is fabricated with a film of lithium of a thickness of30 mm, a polymer electrolyte made of a complex of ethylene polyoxide ofa mass of 9×104 and lithium bis-trifluoromethanesulfonylamide (LiTFSI)to obtain a ratio of the number of is oxygens of the polymer on thelithium ions of 12:1. The solution in a common solvent is spread,evaporated and dried to form a film of a thickness of about 80 μm. Thepositive electrode comprises a mixture of 40% v/v of lithium rhodizonateas prepared in example 1, 5% by weight of carbon black (Ketjen Black®)and 5% v/v of the electrolyte of the electrolytic composition previouslydescribed, but obtained with a polymer of a molecular weight of 10⁵.Acetonitrile is added to the mixture, and the suspension obtained ishomogenized by agitation with zircon balls in a stainless steelrecipient for 24 h. The electrode is obtained by spreading thesuspension on a stainless steel disk of 1.6 cm diameter to form afterevaporation of the solvent, a layer of a thickness of 60 mm. The batteryassembled in a neutral atmosphere (helium<1 ppm O₂, H₂O) in the form ofa battery-button by pressing the three components:anode-electrolyte-cathode and is tested at 80° C. in slow voltammetrywith a digital potentiostat Macpile®. Two domains of activitycorresponding each to a capacity of 305 mAh.g⁻¹ are apparent at about2.8 V and about 1.8 V with respect to the couple Li⁺/Li^(o). Forcomparison purposes, the capacity of a manganese spinal based electrodeLiMn₂O₄ possesses a theoretical maximum capacity of 153 mAh.g⁻¹ at 2.9 Vand modifications of this compound, in order to limit the dissolution ofthe manganese, such as the composition Li_(1.05)Mn_(1.85)Al_(0.1)O₄,have a capacity of 115 mAh.g⁻¹.

Example 3

Tetrahydroxybenzoquinone is treated with an excess of lithiumisopropoxide in solution in isopropanol to give the lithium tetra-saltcorresponding to the following reaction:

C₆(O)₂(OH)₄+4LiOCH(CH₃)₂→C₆(O)₂(OLi)₄+4HOCH(CH₃)₂

The black precipitate is filtered, dried and protected from exposure toair.

A “rocking chair” or “lithium ion-type” battery is fabricated byproviding a graphite negative electrode (85% v/v) bonded with acopolymer of vinylidene fluoride and hexafluoropropene (PVDF), depositedon a thin sheet of copper (8 mm) and corresponding to a capacity of 3.1mAh.cm⁻² for the composition LiC₆. The positive electrode is a mixtureof carbon black of the Ketjen black type (7% v/v), lithium tetra-salt oftetrahydroxybenzoquinone (73% v/v) and PVDF (10%) deposited on analuminum collector of 10 mm. The capacity of the positive electrode fora reversible exchange of two electrons per molecule is 3.5 mAh.cm⁻². Theelectrolyte is made of a 1M solution of LiPF₆ in a mixture of ethylenecarbonate of 2-tertiobutoxyethyl-2′-methoxyethylether (50/50 v/v). Theliquid is immobilized in a porous membrane (Celgard®) of a thickness of25 mm. The battery is charged in an intentiostatic mode at 0.45 mAcm⁻²for 8 hours and the potential stabilizes at 3.6 V. The capacityextracted during discharge at C/5, i.e. 5 hours to extract the nominalcapacity, is of 3.8 mAh/cm², and stable during cycling for over 100cycles. The irreversible capacity of the first insertion of lithium inthe carbon, which is necessary to the formation of a passivation layer,is obtained by over-oxidation of the lithium salt according theequation:

Li₄C₆O₆→4Li⁺+4e ⁻+6CO

The reversible operation of the battery takes place according to theequation:

<Li₄C₆O₆>+2<C₆>

<Li₂C₆O₆>+2<LiC₆>

A generator identical to that of example 3 is fabricated by mixing twoactive compounds in the positive electrode, that is to say 0.9 mg/cm² ofthe lithium tetra-salt of tetrahydroxybenzoquinone and 16 mg/cm² ofcobalt and lithium oxide LiCoO₂. The generator is charged at 4.2 V andits cycling capacity is 2.5 mAh.cm⁻², which corresponds to 96% of thecapacity of the cobalt oxide alone.

Example 4

Potassium rhodizonate K₂C₆O₆ (Fluka) is treated to make anelectrochemical generator in the conditions similar to those of example2. The capacity is 210 mAh.g⁻¹, which is 93% of the theoreticalcapacity, which is 225 mAh.g⁻¹.

Example 5

Copper rhodizonate is prepared by reacting 3.5 g of dihydratedrhodizonic acid with 3.5 g of dihydrated copper acetate in methanol.After evaporation of the solvent and the acetic acid produced by thereaction, copper rhodizonate is dried at 110° C. under primary vacuum.The capacity obtained in a generator comprising a lithium anode and agel-type electrolyte (45% copolymer of vinylidene fluoride andhexafluoropropene, 55% solution 1 M of LiBF₄ in γ-butyrolactone is of450 mAh.g⁻¹ and corresponds to 94% of the theoretical capacity for 4electrons between 3.3 et 2.5 V vs. Li⁺/Li^(o).

Example 6

The compound

is obtained by reacting two equivalents of the lithium di-salt of thecyanamid Li₂NCN on tetrafluorobenzoquinone in DMF. The lithium fluorideis separated by centrifugation and the blue lithium salt correspondingto the above formula is precipitated in ether. This compound possesses acapacity of 235 mAh.g⁻¹ at 2.6 V vs. Li⁺/Li^(o).

Example 7

Rufigallic acid is prepared according to the method of Robiquet (Ann.19, (1836), 204) by condensing gallic acid in concentrated sulfuricacid. The hexasubstituted lithium salt is prepared by suspendingrufigallic acid in THF under a neutral atmosphere and treatment withlithium isopropoxide. The resulting salt is filtered and dried under drynitrogen. Oxidation to the diquinonic form is performed by treating 4.0g of this compound with a stoichiometric amount of[bis(trifluoroacetoxy)iodo]benzene (10.18 g) in acetonitrile. Afterfiltration and drying, the following compound is obtained:

This compound has a reversible capacity of 358 mAh.cm⁻² between 2.5 and3.2 V vs. Li⁺/Li^(o).

Example 8

1.40 g of trans-trans muconic acid (Sigma) are treated with 0.739 g oflithium carbonate in methanol. After evaporation and vacuum drying, agenerator similar to that of example 2 is fabricated by using a cathodicmixture of 25% v/v of lithium muconate, 10% of Ketjen black and 65% ofpolyelectrolyte. The compound has a reversible capacity of 0.8 electronper formula at 1.3 V with respect to lithium. This compound can be usedas a negative electrode in lithium-ion type batteries.

Example 9

A polymer possessing conjugated azino functions (diazo in a reducedstate) is prepared by action of 5 g of hydrazine monohydrate N₂H₄.H2O onthe sodium salt of dihydroxytartric acid (22.6 g, Janssen Chemicals) inacetic acid, under agitation for 24 hours. The dark brown polymer isprecipitated in isopropanol, separated by filtration and dried. Thecompound possesses redox properties of 2 electrons per repetitive unitof the polymer, that is to say a capacity of 290 mAh.g⁻¹. The lithiumsalt obtained by passage through an ion exchange column has a capacityof 360 mAh.g⁻¹. The formula of the polymer reduced to 50% of itscapacity is:

Example 10

The potassium salt of dithiosquaric acid is prepared by reactingpotassium hydrogenosulfide (14.43 g, Alpha) ondibutoxy-3,4-cyclobutane1,2-dione (22.62 g Aldrich) in ethanol. A yellowsalt is obtained and recrystallized in a mixture water-ethanol, and isof formula:

To 18 g of this salt in suspension in acetonitrile are added undermechanical is agitation a solution of tetrabutylammonium tribromide(34.6 g) in acetonitrile. After one hour, the yellow precipitate isfiltered and dried to give:

This compound possesses a reversible capacity of 385 mAh.g⁻¹ at anaverage potential of 2.8 V vs. Li⁺/Li^(o) and its solubility inelectrolytes like propylene carbonate and its mixtures or the polymerssolvating based on ethylene polyoxide is negligible, contrary topolydimercaptothiadiazole.

Example 11

A Schiff polybase, poly(thiocyanic) acid, is prepared by reactingthiophosgene on thiourea in propylene carbonate in the presence ofpyridine. The dark brown suspension is poured in 100 ml of water and theprecipitate is filtered and washed with water. The product correspondsto the composition [C(SH)═N]_(n) with a developed formula:

The polymer in its reduced form is oxidized by iodine in solution inacetonitrile in the presence of pyridine, and the suspension remainingis washed with acetonitrile until a colorless eluate is obtained. Thebrown-black powder corresponds to the oxidation of the thiol groups togive the polymer:

An electrochemical generator similar to that of example 2 using apositive electrode containing 40% v/v of the compound thus obtainedshows a capacity of 360 mAh.g⁻¹ between 3 and 2.4 V vs. Li⁺/Li^(o), thatis to say 75% of the theoretical capacity which is 478 mAh.g⁻¹.

Example 12

In the same manner as in example 11, the alternate copolymer of formula:

is prepared by replacing thiourea with the thioamide of cyanoaceticacid. The polymer obtained after oxidation is a black powder having acapacity of 555 mAh.g⁻¹, with 50% between 3.2 V and 2.4 V vs.Li⁺/Li^(o).

Example 13

Tetraminobenzoquinone is prepared according to the method of Wallenfel &al. (Ann. 1963, 667). 16.8 g of this compound and 2.46 g of chloranil(tetrachlorobenzoquinone) are mixed in a ball mill, and heated underargon at 250° C. in a Büchi TO51 oven followed by a treatment at 350° C.under vacuum. The compound obtained corresponds to the polyquinone-azineof formula:

The lithium salt of this compound is obtained by treating a suspensionof the polymer with a solution of lithium isopropoxide in isopropanol.This compound has a reversible capacity of 345 Ah.g⁻¹ between 2.4 and 3V vs. Li⁺/Li^(o), that is to say 75% of the theoretical capacity whichis 420 mAh.g⁻¹. The lithium salt of this polymer can also be obtaineddirectly by reaction of tetrachlorobenzoquinone on lithium nitride inthe molar ratio 1:2 by cogrinding in anhydrous DMF.

Example 14

A polymer perfectly alternated between ethylene and carbon monoxide isobtained according to the method of Hiraguri et al. (J. Am. Chem. Soc.,1987, 109, 3779). 56.06 g of this polymer are dissolved inhexafluoropropanol and treated with 10.39 g of lithium nitrite underreflux. The conjugated polymer appears under the form a blackprecipitate which is the lithium salt of formula:

Example 15

Azino(bisacetique) acid is prepared by reacting hydrazine hydrate in astoichiometric amount with glyoxylic acid (Sigma) in isopropanol. Theyellow-orange precipitate is dried and filtered, and the lithium salt isprepared in a solution methanol-water (50:50) by adding a stoichiometricamount of lithium carbonate. The salt is dried under vacuum and testedin conditions similar to those of example 7. This compound has areversible redox activity at 1.7 V with respect to lithium.

Example 16

A polymer of the polyamide type of formula:

is obtained by polycondensation of methyl oxalate with 1,4-phenylenediamine in DMF. The reduced polymer is transformed in the oxidizedquinoneimine form by reaction with bis[(trifluoroacetoxy)iodo]benzene indichloromethane. The product has the developed formula:

It has a redox couple at 2.7 V vs. Li⁺/Li^(o) for a capacity of 310mAh.g⁻¹ (theoretical 347). Similar polymers are prepared by reaction oftrifluoroethyl fumarate on 1,4-phenylene diamine (2.7 V vs. Li⁺/Li^(o))or oxalyl chloride on 3,6-diamino pyridazine (2.9 V vs. Li⁺/Li^(o)).

Example 17

A redox polymer is prepared by condensing fumaryl chloride onN,N′-dimethylhexamethylenediamine in solution in DMF, in the presence oftwo equivalents of pyridine. The polymer is precipitated in water andpurified by dissolution in acetone and reprecipitation in methanol. Thispolymer, mixed with carbon black, shows a redox activity at 1 V vs.Li⁺/Li^(o) for a capacity of 195 mAh.g⁻¹ (theoretical 247).

Example 18

In the same manner as in Example 10, a redox polymer possessing an ionicconductivity and produced by the polycondensation of oxalyl-diimidazoleon 1,8-bis(methylamino)-3,6-dioxaoctane (Janssen) in DMF is prepared.This polymer also shows a redox activity at 1 V vs. Li⁺/Li^(o). At theneutral state, the polymer possesses complexing properties towards saltsand an ionic conductivity facilitating the redox reaction. The structureof this polymer in a partially reduced state is

An amorphous copolymer can be obtained by using a mixture of thepreceding amine with 1,5-bis(methylamino)-3-oxapentane. In the samemariner, the oxalyl groups can be substituted with fumaryl or muconylgroups.

While the invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodifications, and this application is intended to cover any variations,uses or adaptations of the invention following, in general, theprinciples of the invention, and including such departures from thepresent description as come within known or customary practice withinthe art to which the invention pertains, and as may be applied to theessential features hereinbefore set forth, and as follows in the scopeof the appended claims.

1.-16. (canceled)
 17. A redox electrode material comprising in whole or in part, a redox compound having at least one oxidation state, wherein said redox compound is selected from the group consisting of: a rhodizonic acid salt represented by the formula (I):

a rufigallic acid salt represented by the formula (II):

an elagic acid salt represented by the formula (III):

a salt of 1,2-dimercaptocyclobytenedione (dithiosquarique) acid represented by formula (IV);

a salt of 1,5 dihydropyrimido[5,4d]pyrimidine 2,4,6,8(3H,7H)tetrone represented by the formula (V);

a salt of a dicarboxylic acid comprising groups linked with conjugated segments corresponding to the formula (VI);

wherein L is independently CR⁵, N or C—CN, and wherein R⁵ is hydrogen, C₁₋₁₂ alkyl, C₂₋₁₂alkenyl, C₆₋₁₀aryl, C₆₋₁₀aryl C₁₋₁₂alkyl, C₁₋₁₂alkyl C₆₋₁₀aryl optionally substituted with one or more oxa, aza or thia of from 1 to 30 carbon atoms, and wherein two R⁵ can form an aliphatic cycle, an aromatic cycle or a heterocycle containing from 4 to 8 carbon atoms when both L are CR⁵; a salt of formula (VII):

a salt of formula (VIII):

a salt of formula (IX):

a salt of formula (X):

a salt of formula (XI):

a salt of formula (XII):

a salt of formula (XIII):

a salt of formula (XIV):

a salt of formula (XV):

a salt of formula (XVI):

a salt of formula (XVII):

oxidation compounds of aforesaid salts of formulae (I) to (XVII); being understood that: in aforesaid formulae (I) to (XVII) M⁺ represents an alkaline metallic cation, an alkaline-earth cation, a transition metal cation, a rare earth cation, an organometallic cation, an organic cation of the <<onium>> type, a repetitive unit of a cationic oxidized conjugated polymer, or a monomeric or polymeric cation optionally having a redox character; and M⁺ satisfies with formula n/pM^(p+) where n is the above mentioned number of cation atoms or molecules given for aforesaid salts and p is the valency of the above mentioned cation atoms or molecules; and in aforesaid formulae (I) to (XVII) the oxygen atoms with a double bond can be replaced with a group —NCN or —C(CN)₂ and oxygen anion O⁻ can be replaces with a group N⁻—CN or C⁻—(CN)₂.
 18. The material according to claim 17, wherein the rhodizonic acid salt is lithium rhodizonate, potassium rhodizonate or copper rhodizonate, or their reduction products.
 19. The material according to claim 17, further comprising at least one electronic conductor and at least one binder.
 20. A material according to claim 19 wherein the electronic conductor comprises carbon black or graphite powder, and the binder comprises polytetrafluoroethylene, co- or ter-polymer of ethylene, propylene and a diene.
 21. A material according to claim 17 characterized in that it can be used as a source of lithium to compensate for the inherent losses caused by the formation of passivation layers by the electrodes.
 22. A material according to claim 21 comprising derivatives corresponding to the following redox anions: 